The purpose of this project is to continue assess the neuropsychiatric status of HIV-positive individuals who have abused drugs over a long period of time. There exists very little data on the impact of drug abuse on the brain structure and on the cognitive status of HIV positive individuals. This protocol will include 60 HIV positive participants who do not show any overt signs or symptoms related to AIDS. Data collected from the HIV positive individuals will be compared to 60 matched seronegative individuals with similar drug history. We are testing the hypothesis that a HIV status might exacerbate the neurological status of drug using individuals. For example, we have found that drug-using HIV-negative individuals have abnormal eye movements, increased frontal release signs and decreased reflexes. In addition, these individuals have abnormalities on neuropsychological tests of attention, and memory. Moreover, MRI scans show decreased volume of the frontal lobe in drug abusing subjects. We are predicting that HIV positive individuals will have more abnormalities than HIV- negative subjects.